The Training Program in Environmental Health Sciences at the Johns Hopkins University Bloomberg School of Public Health (BSPH) is interdisciplinary and interdepartmental, involving forty-one faculty from four departments of the School: Biochemistry and Molecular Biology, Environmental Health Sciences, Epidemiology, and Molecular Microbiology and Immunology. Support is being requested for 23 predoctoral and 3 postdoctoral trainees. The overall goal of this training program since its inception has been and remains: to provide students with the theoretical and conceptual background through didactic course work, research training and completion of an independent PhD thesis dissertation relevant to the field of environmental health sciences. The purpose of this goal is to enable students to develop independent careers aimed toward the discovery of new knowledge and/or the application of new knowledge to prevent disease and improve health in human populations. This program has several strengths. First, it has a long history and track record of training pre- and postdoctoral trainees who have been successful in obtaining important career positions in academia, industry and government. Second, it is located in a school of public health where emphasis is placed on the discovery of new knowledge of mechanisms of cell processes and toxicity coupled with its application to prevent disease and improve the health of human populations. The latter mission is realized through measures of exposure and identification of biomarkers of exposure, susceptibility and early biological effects leading to disease, with the collective goal of developing strategies for preventive interventions. The BSPH includes faculty and students with interests in each of these steps and places emphasis on prevention of disease in populations as opposed to individuals. Third, the interdepartmental/interdisciplinary composition of the training faculty provides for interdisciplinary doctoral training. The research programs of the individual training faculty have been categorized into seven research areas that encompass various disciplines and range from studies at the chemical, biochemical and molecular levels through the cellular level to the use of whole animal models and the study of human populations. Fourth, the interaction and cohesiveness of the interdepartmental programs is facilitated through several mechanisms. First, the three laboratory departments participating in the training program share a joint recruitment program. Second, all predoctoral trainees take a common core of courses that provide both a firm foundation in environmental health and exposure to the broader field of public health and research ethics. These courses include: "Principles of Toxicology", "Environmental Health", "Public Health Perspectives on Doctoral Research" and "Research Ethics". Third, all trainees participate in three meetings each year where advanced pre- and postdoctoral trainees present the results of their research. Fourth, all trainees participate in an annual scientific workshop, an event co-sponsored by the Training Program and the Johns Hopkins Center for Urban Environmental Health.